If the return on stock A in year 1 was -3 %, in year 2 was 1 %, in year 3 was 20 % and in year 4 was -6 %, what was the standard deviation of returns for stock A over this four year period? (Round your answer to 1 decimal place and record without a percent sign. If your final answer is negative, place a minus sign before the number with no space between the sign and the number)